One of the arguments one regularly sees against the death penalty is its supposed cost, which we can paraphrase as "It's cheaper just to hold a convicted murderer in prison for life than to spend money on lawyers handling the litigation over his death sentence."
There's a certain chutzpah to this: after all, it's the very people arguing against the death penalty who are forcing governments to waste millions of dollars dealing with collateral attacks on death sentences, in conjunction with judges that ignore the law in assisting that effort through multiple levels of appeal. (Here, I'm distinguishing between those who challenge death penalties on technicalities and public-interest firms like the Innocence Project that are usually acting to exonerate the incorrectly convicted.)
But I've always thought that the cost argument just simply wasn't true. If the death penalty disappeared tomorrow, the hundreds of lawyers who fight the death penalty wouldn't rest on their laurels. They'd simply shift their focus to other attacks on the use of criminal justice to punish criminals. Governments would still be spending the same millions of dollars defending against collateral attacks on convictions; they'd just be spending it on a different set of convicted criminals. Any monetary savings from abolishing capital punishment would be illusory.
Hans Bader's recent post (discussed below) suggests my theory is not only true, it's producing accurate predictions: this term's Court will decide Miller v. Alabama and Jackson v. Hobbs, cases involving life sentences without parole. As some states have moved against the death penalty, the anti-punishment wing of the bar has now opened a second front against life sentences, already with some success in Graham v. Florida.